Fluid-actuated reciprocatory device



Fatented July 13, l.

rse s i, sane FLU-IB-ACTUATED' RECIEBG CATORY DEVCE.

Application led March 27, 1820. Serial No. 369,689.

This invention relates, generally, to the construction and mode of operation of fluid?- pressure-actuated mechanisms of various types, and it is particularly adapted for .se in air driven percussion tools, such, for errampl'e, as impact drills and pneumatic ham.- mers or riveters which comprise a.V cylinder havingv` therein aY free piston` member that is.- reciprocated at a: high speed to deliver a rapid. series of blows against another rel:- atively stationary member (such as a drill `stem or ri-vet set). located.V at one end of the cylinder.

rl-"he general objects of my. invention are to.` greatly. improve the operative design and the Working performance of tools of this character; and te these ends my' improvements areV directed. t@ the provision` ofy a light, strong and` powerful mechanism. that can bel readily used-in any position, and to the more effective and efficient utilization of the Workingv fluid, sor as to not only increase the speed of action and the driving power ofthe tool, but also decrease its consumption of. Working fluid` per unit o'fpotver developed;

More specifically stated', my invention is designed to provide a pneumatic hammer of minimum Weight and size, which.. can lbe readily carried from place to place, and used with a minimum. amount of .fatigue by the operator, and which Willhave a maX- imum effectiveness both in` increasing the i force and the ra idit of iston im aact P against the rivet rseit (or other-tool element) and: also in decreasing the recoil or rebound action which tends to diminishl the effectiveness of the blow, and which is also capable of being actuated with a less amount of work-ing fluid` than is required for other hammers ofthe same rated capacity. rEhe advantages of these 'features of my improvements are very important vbecause they enable the users of these tools to greatly increase their Output; and also because they considerably reduce the expense of the operation and. maintenance both of the hammers themselves and of theY power plant that supplies the motive fluid thereto.

@ther objects and advantages 'of my invention will be made apparent. tov those skilledv inthe art by the following explanation. Ofcertain embodiments of my improvements which are presented as generically illustrative of the manner in Which the said improvements` may utilized in the various `distance greater than its oivn length.

types andr forms of fluidV actuated tools-i-the particular exemplary embodiment herein shown and described being a pneumatic hammer of the form. now commonly employed in riveting` and similar operations.

in carrying out my invention, l, employ a cylinder' having reciprocatory piston therein and having suitable means. for supplying motive fluid to the cylinder to actuate the piston. rEhe cylinder is provided with inlet and exhaust ports at both ends and. a control valve is provided for governing: the ad"- mission and exhaust offiuid pressure to and from the piston chamber.. The piston is moved on its power stroke by the direct action of the live motive fluid flowing into the cylinder from themain supply reservoir and in the practice of my invention a portion off the charge of live motive fluid, Which actuates the piston on its power stroke, is segregated in a separate chamber and utilized for returning the piston on` its reverse stroke this being, as l believe, a broadly new method or manner oi' actuating the reciproeating piston member.

As hereinbefore suggested my invention is peculiarly advantageous in connection With riveting hammers and like tools which are usually actuated by compressed air, and the invention is especia-ily, though not essentially, adapted for application to a pneumatic riveting hammer of the long stroke type, in which the piston reci'procates a In such tools the return of the piston has heretofore been effected by the admission of a fresh charge of live motive fluid vfrom the main supply reservoir and the result of the action thereof on the piston was to graduallyY accelerate its speed during `its return stroke, so that the maximum velocity was attained at the end of such stroke g. and a severe shock Was produced by the stoppage and reversal of the movement at the Vrear end of the piston chamber.

My method of operation differs from that just described in that, instead of admitting a fresh charge of live motive fluid for operating the piston on the return stroke, l utilize, for this purpose, the expansion of a segregated portion of the same charge of motive fiuid that actuates the piston on itsv power stroke. rihe result of this is that the return movement is more promptly initiated, but the velocity of this movement 1s gradually decreased and is lowest when the piston reaches the rear end of the piston chamber. Under such conditions the shock of reversal at the termination of said movement is greatly reduced.

The use or" a single charge ot live motive fluid to move the piston both on its power and ret-urn strokes also effects a. considerable saving in live motive Friuid Without di1ninishing the poiver developed on the ivorling stroke and ivithout sacrificing any of the advantages incident to the old mode of operation.

The accompanying' drawings illustrate several specific foi-nis ol pneuniatic hammer constructions each of which constitutes an exemplification of my generic invention. in these drawings:

Figure 1 is a longitudinal sectional view through one form of tool embodying my present improvements.

Fig. 2 is an enlarged sectional vien' of a part or" the construction shovvn in 1 but showing the fluid cont-rol valve in another position.

Fig. 3 is a transverse section taken the plane of line of Fig. 1 viewed in the direction of the arrovvs.

Fig. 4 is an enlarged sectional detail view et a portion of the inner cylinder shoiving one form of check va ve which is used in certain applications of my invention.

Fig. 5 is a perspective vieiv of the said check valve member.

Fig. 6 is a longitudinal sectional vier: through another form of pneumatic hammer that also `embodies the general features of my present improvements.

Fig. 7 is an enlarged sectional vievv shoiving the fluid control valve ot this second construction in position to etlect the re rn stroke. o1" the piston.

Fig. S is a detail vieiv showing another form of fluid check valve that is employed in the organization depicted in T and S. and Y Fig. 9 is a longitudinal section through the front end of still another tool which embodies my invention.

Fig. 10 is a fragmental longitudinal .sectional vievv through the front end et still another tool. ivhich embodies my invention.

In the construction slioivn in Figs. 1, to 5 the body of the tool composed of outer and inner tubular members 10 and 11. vvithin the inner one of which the piston 1Q reciprocate?. At the forward end oi the tool a rivet set bearing sleeve or holder 153 which is secured to the outer tube 1() and supports one end of the inner tube 11. and vvhich is adapted to receive the shunt; oi. a suitable rivet set 11 against ivhich the piston is arranged to abut on its vforward or pov-7er stroke.

At the opposite end of the tool is a handle 15 which has a tubular head or sleeve 16 that is screived over the rear end of the body portion of the tool and is loci-:cd in place thereon by any suitable mear s, as a ratchet ring 1T, that engages i. .th ratchet teeth on the end et the sleeve 16, and is held from turning by the eccentric head of an adjustable (rotatable) d pin 17a. Any suitable form ot rc einer. such as an annular spring clip 1S may be utiliAe-'l to secure the parts 1T and 1T in place; in the particular construction under consideration this clip 18 also serves as a gruerd ring or defiector for controlling and directing the escape of the exhaust troni the piston chamber.

The rear end of the outer tubular .iember 10 is bored out to receive a tivo-parl valve box which consists of a front ser-- tion 19n that engages the rear end of the inner tube 11, and a con'iplementary section 19b vvliich engages the section 19 and projects rearwardly into the recess in the liandle head. These complementary sections 19a-19b are bored and finished to receive a reciprocatory valve member Q0 of tubular or annular form, Which is provided with three projecting ribs or flanges 29, 30 and 31, and Which is adapted to control the openings ot certain inlet and exhaust ports, and thereby govern the admission and escape ot motive tiuid, in a manner which will be presentlj.' explained. In the present instance the rear end of the inner tube 11 is supported by the front end ot the valve box 19 and terminatesl in trout of the valve member 20. but said tube may, if desired, be continued through the valve be); member to the rear end of the piston chamber.

The space Q1 between the outer and inner tubes 10 and 11 (the ends ot which space are closed respectively by the rivet .set hearing member 13 and the valve box section 1)) constitutes a storage chamber which i adapted to receive and segregate a portion o the live charge of motive fluid that parses from the interior of the inner cylinder through ports Q2 in the ivall thereof. when the said ports are uncovered by the formo-d niovenient of the piston. These ports ma).v he controlled a check valve Q3 that alloivs an outward floiv of the motive fluid from the piston chamber into the chamber 2l hut prevents a reverse flow 'trom the said chamber inivardly.

The exemplary check valve 23 shown in the tigs. 1.. 3. and 5 is in the forni ot an annular band, ol' arched cross section. which is seated in ay groove @l in the inner tube 11 and which is divided or split. as at Q5, lo give greater circumferential resiliency and enable it to he readily sprung into place in the groove Qi. Preferably.' the hand is also provided vvith a series of open end slots QG in its edges to increase its transverse resiliency and permit it to yield easily to the f' i i llU lli

outward pressure of the motive dfluid inthe piston chamber. Any suitable means-such as a pin 27-ixed in the tube 1l .and entering an'aperture28 in the band-may be used to secure this valve against accidental dis-V placement. l

The handle is provided .With a supply passage 32 which is controlled by a valve.33 operated by Aa thumb lever 34 in the usual The inner end of this passage `opens into the .annular chamber '35 which surrounds lthe rear portion fof the valve boX 19h.

This Vchamber is lin yconstant communication-through one or Vmore small ports the flange 29, of the valve 20, reciprocates. The lWall of the valve 20 is provided With la suitable number of small ports 38 which -20 is in its forward position, as shown in =Fig.f2,these ports being cut o :by the valve member 2O when in :its rearmost position, shown in Fig. `1.

The forward end of the .annular chamber 21 is in communication With the front endv of the piston .chamber through a circumferential row of lradial ports 40; .and the rearfend of this chamber is connected-Lby one or more longitudinal passages 41-ivith the lannular lchamber 42, -that is zformed .between the inner Wall of the valve box and the outer Wallof the 'valve-,member 2O and its flanges 30,31. When the valve member 20 is in Iits forward position, shown vin Fig. 2, this chamber `42 is Vin. communicationvvith a series `of radial ports 43 leading .through v.the valve 'box and kc,onnnunicating Ia-t their outer ends vvith an annular chamber44 formed .between the valve :box and the Outer cylinder. This chamber v4'4 ,is in .constant communication with the atmosphere through a. suitable number of ports 45 which cpeniinto a space covered by .the spring -clip 18, the latter having ports '46, therethrough to permit the `escape 4of the fluid. Then the valve vmember 20 is in .its rear position shovvnin Fig. l, the chamber Y42 is cut off from the exhaust ports 43 by the flange 3l on @the valve, and a direct communication -is established between said ports 43 Iand the piston chamber so as to permit the .exhaust of thefeXpended charge ,of-motive Ifluid ffrom therear end of the picton chamber upon the return stroke of the piston.

VIn order zto prevent any trapping of air :in 'the chamber in front ofthe valve `flange 30, I provide 1a small vent A41, which rom anunicates at one end with the exhaust cham- '.ber 44 and at its other end `with thechaminner Wall of the valvebox in such position vthat it will be closed by the Avalve flange when the valve member is in its forward position,.sho\vn in Fig. 2, but Will be put into communication with the chamber 42 assoon as the said valve member starts 'to move. rear- Wardly.

The operation is as follows: When the thumb lever 34 in the handle lis .pressed dovvn the live motive fluid will be admitted to the main supply chamber and will act on the rear face of the flange 29, lto move the valve forwardly kinto the position shown inFig. 2. A charge yof motive fluid is thus admitted through the inlet ports 39'into the piston chamber, and the piston is vdriven forwardly thereby. The previous dead air which is in front ofthe piston, and in the storage chamber 2l, escapes lto the atmosphere through the ports and passageways 40, 2l, 4l, 42, 43, 44, 45, and 46. As soon as the piston passes the. escape ports 22 in the inner tube il, a portion of the live charge of motive fluid escapes therethrough past the check valve 23 and into the conduit 2l until the pressure in the said conduit is substantially equal to that in thel piston chamber. This segregated charge passes through the ports 4l into the chamber 42 andexerts a combined static and .kinetic .pressure against the large flange 30of the valve member 20, Which overbalances the pressure in the chamber 37 upon the rear flange 29, and the valve .member 2O Will then be shifted to its rear position, as shown in Fig. l. This rearward movement uncovers the end of the port 49 and-.permits live motive fluid to flow from the main supply chamber 35 through said port 49 4into the chamber 42 and thus assist in shifting the valve, and in maintaining it in .its second position. The linlet ports 39 1willnow be cut olf from the piston chamber andthe exhaust ports 43 Will be open. The live motive fluid which has passed into the storage chamber 2-1 will be prevented from returning to the main piston chamber :by :the action off the check valve v23 and will pass through the ports and exert a pressure upon the forward end of kthe piston to eect .the return stroke of the latter.

As the piston moves rearwardly the pressure of the segregated charge in the storage chamber is progressively reduced by the expansion of the trapped ymotive fluid; and the force acting on the front and the rear .of the reciprocating member is thus progressively diminished, with a resultant slowing down of the velocity of its return movement. The .motive fluid ythat is .admitted to .the chamber 42, through the passageway 4),

will, of course, pass into the chamber 21 (through the passageway/ts lll), and will tend to aid and accelerate the rearward stroke of the piston; but the sizes of the passagewavs 49 and ll are se proportioned that this e'liiect will be relatively insignificant; and the re stricted liow of high pressure. air into the upper. or rear, end ot the s d storage chamber will not sensiblyv interfere with the continued expansion et the segregated charnj and the progressive slowing down of the piston movement on its return stroke.

The relative volumes of the chamber 2l and the piston cylinder are preterablj,v so proportioned that at the rear end et the piston stroke the pressure in the said connected chambers is not nuch above atmospheric. rl`his drop in pressure reduces the torce acting on the first valve flange 30 to such a point that it is no longer able to overcome the live air pressure on the rear of the smaller valve flange Q9; and the valve Q0 will be again shitted forwardly. lt this reduction of pressure on the larger valve flange is not, in itself. sullicien to complete the desired movement ot' the valve, the said action will be supplemented by the closure ot the small vent ports @3S-bj.' rearwardlv moving' piston-and the consequent rapid building up of the pressure in the restricted chamber space 3T to a point where it will be sutiieient to torce the said member to its for vard position, shown in Fig. Q. rl'hc continued rearward movement ot the piston under its own momentum is stopped and reversed b v a cushion ot lluid poclreted in the. rear end ot the piston chamber, and the above described c vcle of operations is continued as long as the admission valve is kept open.

ln the construction shown in Figs. (S-T and S the main bodv. l", ot the hammer is provided with two inner tubes or sleeves ll" and el), the tirst of which constitutes the guide barrel, 'lor the reciprocator;vv piston member l2. This inside guide tube extends the entire length of the hammer and is held in position therein between the shoulder 5l. at the inner end of the rivet set holder '13, and the sott packing' washer 52 thatJ :nav be inset either in the rear end of the handle sleeve 1G or in the adjacent end of the valve box 19a. The intermediate sleeve 50 is supported at its ends on annular collars 53, 5l. which surround the adjacent parts ot' the inner piston tube lla, and the rear end oi' the said sleeve is also engaged h v the Yforward extremitjv of the valve bof; member 1Q, rlhe rear port-ion ot the tube ll is ground and finished, on its exterior surlaee, to receive and guide the tubular distribution valve 20"; and this valve is pro vided with two annular flanges 29:L and S0, which are itted to slide smoothly in the respective chambers Si and 42a ot the valve box 19a. This latter member is provided with series of radial passagesV 391 which leso ir in the annular passage Saa-between the rear end of the valve box and the interior or the handle head 16a-to a chamber 55, in which the extreme rear end of the valve 20 located; and the inner piston tube ll is provi-.Lcd with a corresponding series ot' radial ports, 39h, which communicate with the chamber when the valve is in the lorward working stroke position shown in Fig. G, and which are closed when the valve is in the reverse return stroke position shown in Tlig. T. rIlle valve box lf)LL is also provided th two other ,series ot radial passages, lil l 5G; the first of which is in registi-3Y with e exhaust ports flee in the main bod;y ltr" the hammer, and the second ot' which serve to connect the chamber 2lb between tubular members l0 and 50 with the box chamber lQ The chamber 21" n c-'mmunieation with the front end ot t' e piston chamber through the ring ol ports lt/li; una' when the valve is in the, position showi in Fig. 6 the air or other fluid can i freelyY from that end of the inner tubul'. r neuh through the ports 56, the chaml r l2 and the passageways ll and l5 to e annular exhaust space under the spring Aln dellector 1S, and thence through the is l-G to the external atmosphere. The ol the tubular valve 20 is perforated with a series ot radial ports 57, which are connected at their inner ends by a shallow annular groove 58 on the interior of the valve shell. A cooperating series of ports GO are drilled through the piston guide tube ll, in such position that they register with the groove 59 when the distributing valve is in the rearward position shown in Fig. T, and in such position the rear of the piston chamber is, therefore, in lrce coinmi'inication with the atmosphere through the ports ('tl-ii, the chamber and the exhaust passagewafis, 43a, elfi and /lt The valve box 191 o'i this construction is also provided with two small live air supply passages 3G and which lead trom the main supply chamber 3.3 to the chambers 3T@ and l2 respectively. The first ot these passages is always open, but the forward end ot the second one is closed by the external peripheriv olt the valve tlange S0 when the valve is in its forward position (Fig. (l) and is onl)v opened when the valve is shifted rearwardbv to the return stroke position (Fig. T). The valve member its-elf is also provided with another restricted port 3S which leads into an annular groove 38h on the inner peripheiwv ot the valve shell; and the piston guide tube 1ln is drilled at Gl to form a vent opening which is in registry with the groove 3S" when the valve is in the last described position.

`he forward end ot the piston guide tube ll"L is provided with a series of venturi shaped ports '99 the form of which is best shown .in Fig. ,8. rihe inner enlarged ends of these ports open into the piston chamber at a point vjust baelrof the piston when the latter has completed its forward strolreand VVdelivered its blow on :the shank of .the rivet set la; and the outer contracted endsfthereof open into the space 21a, between the tubes lia and 50, which is v.in constant vcommunication with the valve bor: chamber 42a through one or more ports lla in the collarl.

The' operationof'this last described yconstruction is as follows: lv/When compressed air is admitted to the supply chamber 35E-through the handle passage B2b-the valve i202L is Vforced forward by the flow of the said air throughthepassageway,,36a into thev chamber 37a .behind the `rear valve flange 29a. rlhis opens the inlet ports 391 and admits thelive motive `:liuidto the rearend of the piston chamber to drive :the piston forwardly against the rivet set 1.1i. During this forward movement, the air ,in the front end of the piston chamber, and the vchambers '21@ and 21],is allowed to escape-to the atmosphere through the ports and passageways, la, 43a, tavand 46a. Wlhen the piston, in its forward movement, reaches and coversithe venturi shaped openings 22a the inner storage chamber 21a is cut oil' from communication with the external air; and when the rear `end of the piston passes these openings a portion of the actuating charge of live motive fluid enters this lchamber and 'passes through the ports ila into the chamberinfront of the forward valve flange 30a. The-pressure thus createdon the flange 3()a is in excess of the pressure exerted .on the smaller rear flange 29a, and the .valve member 20@- is thrown rearwardly into the position shown in Fig. 7. This rearward movement of the valve closes the inlet ports 39h, and putsthe cylinder ports in communication with the eahaust ports 5'7--d3`a--fl5aand 46a. It also shuts off communication between the main exhaust passageways an fl the ports 5G and puts the latter in communication with the chamber Qia, thus allowing the live motive fluid in this chamber to lill the space 2lb and pass through the ports Y Oa to the front end of the piston chamber. The sudden release of pressureon the back of the piston-by the Vopening of the eX- haust from the rear end of the piston chamberdand the concurrent application of pressure to the front end thereof (by the iiow of air through the ports 56 into the chamber Qlbl cooperates with the rebound of the reciprocating member from the end of the rivet set to initiate a quick reversal of the piston movement, that will cover the inner ends of the venturi portsila before any large amount of the live motive fluid in the chamber 21a can pass baclr through the restri :ted ends of the said ports and escape to the exhaust. The .segregated portion of the 1original live motive fluid charge which remains Vtrapped in the storage chambers 21a and 2lb gradually.expands as the piston 12 moves rearwardly and thus exerts aprogressively diminishing force on thevreciproeating member; and :the frictional resistance to the piston movement,combined with the retardation by gravity when the hammer is operated in a vertical position-will produce a constant deceleration of velocity `as the piston approaches the end Lk.of its return stroke. Alheaggregate volume ofthe chambers 2l. Yand 2lb is preferably so proportioned to the volume of the piston cylinder, that the pressure therein `has been diminished to approximately that of the external air when the piston has completed its rearward movement; and the ycorresponding fall in pressure on the face of the valve flange 3Ga permits the live air pressure on the rea-r flange 29a to throw the valve Yforwardly, either just before, or Ajust after, the piston vhas reached and covered the small vent ports v6l. This forward movement of the valve again opens the live air ports 39h, and the live motive iiuid passing through these ports to the rear end of the piston chamber cooperates with thev air that has been trapped and cushioned back of the pistou vhen the latter passes the exhaust openings (l0-to quickly reverse the movement of the reciprocating member and Adrive it forward again. 1

ln the two constructions above .described the annular chamber, or chambers, between the outer, or main, barrel of the hammer andthe inner piston guide :tube-serve both as a storage reserve for the segregation of a portion of the live motive fluid charge (for e'ecting the return movement 'of the piston) and also as passageways for the exhaust from the front end of y'the piston chamber during Athe working fstrolie. "IU-his is the form or type of construction which 'I prefer to Vemploy because it eliminates vall necessity for the drillingof long longitudinal passageways through the hammer barrel; and also because it permits of the easy renewal vof the piston guide tube when-the latter becomes worn or otherwise impaired by the rapid reciprocatory `movement ofthe piston member. This construction in also considerably lighter and much less expensive than .the usual solid barrel form of hammer; and it is also one that can be very easily and quickly assembled, or disassembled for .repairs or for renewal ofany injured parts.

The use of my present invention is not, however, dependent upon the employ-ment of the double or multiple tube type of construction hereinbefore described. ln Fig. 9 l have illustrated a modification of the ordinary solid barrel form of structure which is adapted to operate in accordance with my Cil new method of actuation. In this embodiment of my improvements I provide the lower, or forward, end of a solid hammer barrel c with an enlarged head G5, which is rigidly secured thereto in anysuitable manner and whichVi is bored out to form a storage or segregation reservoir 2l? that communicates with the extreme front end of the piston chamber (just back of the rivet set shank L) through the radial ports 110", and which is also in communication with that chamber through one or more valve controlled ports 22C. The rear or handle endL of the hammer barrel 10 is bored out to receive a valve box construct-ion similar to that shown in Figs. l and Q; and the chaniber space 2i@ is connected to the valve bof; pas-Y sages ll by means ofone or Ymore holes GG that aren drilled longitudimilly7 through theV solid side wall-of this barrel. The check va ve used in this construction, to control the port opening 22C, consists of a small steel ball 67 which is held loosely in place bctween theconed or countersunk end of this opening and the adjacent face of the shoulder G7. lThis same form of check valve may be used in the constructions shown in Figs. l to S; in which case the ball element is held in place between the outwardly flared end of the port 22 and the adjacent face of the hammer barrel l0 (as shown in Fig. 10) or between a corresponding shaped port Q2 and the inner face of the intermediate tub 50.

The mode of operation of the construction illustrated inWFigs. 9 and l@ is the same as Y that which generically characterizes the previously described embodiments of my invention; and is specifically the same as that of the structure shown in Figs. l to 5. Then the piston l2 reaches the position shown in Fig. 9 the liveV motive fluid in the rear of the reciprocating member passes through the E port (or ports) 22C and fills the reservoir 2lic and the passageway 66, thereby moving the distribution valve to its rearward position in the manner previously explained. This closes the rear end of the passage 66 and opens: the rear end of the piston chamber to the exhaust; and the resultant drop in pressure back of' the piston sucks the ball valve 67 against its seat and traps a segregated mass of live motive Yfiuid in the reservoirV 21. This segregated charge passes through the-ports and effects the return of the piston by its continued expansion; and the continued drop in pressure thereby produced ultimatelyrreduces the force aetino' on the front flange of the distribution valve to such a degree that the said member is moved forwardly, and one complete cycle of' operations is thus concluded.

The advantages and improved results that are secured by the use of my invention in fluid actuated pressure tools will now-*be appreciated by those skilled in the art. Briefly summarized, some of the more important functional and result-attainingfeatures that characterize my present improvements are as-follows: i

First; the segregation of a portion of the working Ycharge of high pressure motive fluid, near the end of the-forward stroke, in a storage reservoirV that is in direct and Vconstant communication with the front of the piston chamber, results in the practically instantaneous initiation of the return movement of the reciprocating member after it delivers its power blow on the working tool; and this effects a saving of' time that rcsuits in a substantial increase in the number of strokes per minute (for a given motive fluid pressure) and a corresponding augmentation of the driving power; of the hammer.

Second; the return of the reciprocating member by the expansion of' a segregated and conhned charge off high pressure fluid, produces a geometrical reduction in the accelerating torce acting on the rearwardly moving piston, which results in a very marked decrease in the velocity ot that member as itV nearsthe rear end of its stroke This, in turn, nakes it possible to more quickly and easily arrest and rev rse the movement of the piston at the beginning of the next power stroke; and to thus effect. a further saving in time with a resultant increase in working speed. The progressive slowing down of the reciprocating member during its return movement also makes it possible to reduce the cushioning spaceat the rear end of the piston chamber-by locating the main admission and exhaust ports closer to that end-and thus substantially increase the possible effective length of' Ypower stroketor a given length of hammer barreh Third; the progressive decrease inthe actuating pressure on the front end of the piston and the marked slowing down Vorde- 'celeration of that member before the Gush-1 ioning` action begins-which results in greatly reducing the final compressive press-uril produced by that action eliminates, or very greatly reduces, the back kick or recoil of the hammer against the hand of the workman, and Vthus enables him to more effectively hold it in driving position, and operate it with less muscular strain and fatigue.

Fourth; the segregation of' a portion of the working charge of live motive fluid during the power stroke of the hammer. and-the utilisation et' that segregated portion to return the piston by expansion. results in an increased economiy and efiiciency in operation; not only becausel of the saving in the volume of compressed air used foreach reciproeation, but also because of the cooiing effect, prod .ced by the expansion of the working charge in the hammer barrel-particularly on the rivet set end thereof-which 'limitation ofi my i vention "andthe effect under consideration is of particular advantage and importance when the eizliaustuports become clogged or obstructed WithV oil or dirt-as not infrequently happens inthe useof tiese tools;

Sixth; my improved mode of operationof actuating the piston in both directions by a single Working charge of air, and ellectingn adeceleration or a' progressive slowing dovvn of the piston Y movement on the return stroke-enables me to simplify the design and construction of the mechanical organization, and thereby reduce the first cost of manufacture'. lt also maires itr possible *to-reduce the diameter and length of the tool-as compared with those heretofore in use-and to thus' substantially decrease the Weight and hullr` of a hammer ofi given rated capacity or driving' power; thereby facilitating the manipulation of the tool eiicl'enahliiig the operator to use itin very cramped andv confined quarters.

Seventh; the increased facility and ease ofimanipulatioii,-due in'part tothe lighter Weight andin part Vto the decrease in vibrationand recoil shock-the augmented driving` pow r (resulting)` from the greater number of strolresrper minute) g and the higher degreeof economy and efficiency in theuse of' motive fluid; allmutually cooperate to very substantially increase the Working apacityof fluidt actuated pressure tools which areconstrncted and operated in cordauce With-my present invention; and to correspondingly decrease hoththe first cost and the'continued expense vofY maintenance the power plant and the battery equipment required to perform a given amount of' Work.

Vilhilel have in the foregoing description gone 'into considerable detail relative to the particu-lar constructionsl of the exemplary tools shown` in the draivingsit should be understood that this minute description has been `given for the purpose of lucidity only andis not in any Way to be construed as a The tools shovvn and described arefonly ay few of many structures which might he einployedin practicing my invention; and it is only'hecause the present improvements are especially` advantageous in connection fariouswith pneumatic'hammers that l have shown and described them as so applied. Asindi-v cated above many different arrangements ofthe storage chamber and the piston chamer, and various forins of control and distribution valves andf valve boxes, may be used in connection With the present development; and these and other details of con-- struction may be varied Widely Without deff parting. from the scope of my invention.

It should also loe noted that in my copending application Serial No. 483,7 l, filed July ll, 1921, l have claimed the specific structural or mechanical relation between. the outer and'inner tubular members and the valve-hoz; herein illustrated, as Well as the structural relation between those elements and the handle-portion. of the tool and they specific means employed for locking those elements together and guarding` the locking means; consequently such structural. details are not claimed herein.

l claim as my invention: Y

l. A method of reciprocatingpistons of pneumatic tools, which compri-es the for- Ward movement of the piston by theappli cation of alive air charge to the reari ofthe piston andthe concurrent expulsion of fluid frornthe front thereof, the mining of portion of the live air charge Withthe expelled fluid and' the utilization of the increased pressure thus produced in the mixture to initiatevthe rearward stroke of the piston.

Thmethod of reciprocating` the pist-on of pneumatic tools Which comprises the forward actuation of the pistonv hy a charge ofv motive fluid applied to the rear ofthe piston, the concurrent expulsion of fluid from th front thereof, the increase in pressure in the escaping lluidby mixing it with a portion of the charge of fluid from the rear of the piston, and the utilization of the increased pressure thus produced to initiate the rearward stroke of the piston.

rl`lie method of reciprocating the piston of pneumatic tools which comprises the forward actuation ofthe piston by motive fluid applied to the rear of the piston, the concurrent expulsion of fluid from the front thereof, the increase in pressure in the fluid so=1 expelled hy mining' it With a portion of the charge of motive fluid from the rear of the piston, and the utilization of the increased pressure thus produced to concurrently confinefthe mined charge and utilize it in' the initiation of the `rearward movement of the piston. y

Ll. The method of operating'flluid driven' percussiontools which comprises thelforivard actuation of a: reciprocating` piston member hy a charge of high pressure-motive fluid applied to the rear ofthe piston7 the concurrent expulsion of fluid from the front thereof, the mixing` of a portion of the high'presk Vsure flu d charge with the fluid so expelled and the utilization of the mixed charge in concurrently actuating the charge admission valvc and in initiating the rearward movement of the reciprocating piston.

The method of operating fluid driven percussion tools which Acfmiprises the forward actuation of the reciprocating piston men'ilier oy a charge of high pressure motive fluid :viplied to the rear of the piston, the mincurrcnt er. iulsion el fluid from the front of the piston chamber. the increase in velocity of the fluid so expelled by mixing therewith a portion of luga pressure fluid charge and the utiliization of the increased vel city thus produced in trapping the mixed fluid in front of the piston.

The method of reciprocating a valve controlled detached impact piston of a fluid actuated tool having a charge admission valve, and of actuating the valve, which comprises the forward actuation of the piston by a charge of high pre se motive fluid applied to the rear of the piston through the valve, the concurrent exiliulsion of fluid from the front ol' the piston, the mir-:ing of a portion of high pressure fluid, from the rea of the piston with fluid so expelled and the utilization of the mixed chare'e in concurrently actuating the valve to trap the mixed charge and in initiating rearward moven'ient ofthe piston.

The combination with the cylinder and detached piston of a fluid-actuated impact tool` of an annular chamber surroundingthe cylinder and communicating freely therewith at its forward end; a valve mechanism at the rear end of the cylinder for controlling admission of the motive fluid behind the piston to produce the working stroke and for also controlling the venting of the cylinder in front of the piston through said chamber and for venting of the cylinder behind the piston; means for entrapping fluid from the cylinder ii said chamber during the worl-zing stroke; means for admitting fluid so cntrapped to shift the valve to cause return of the piston by such fluid; and means controlled by the returning piston for causing' reverse shifting of the valve to initiate another ivorl-:ing stroke.

S. A method of reciprocating pistons of pneumatic tools, which comprises the forward movement of the piston by the application of a live air charge to the rear of the piston and the concurrent expulsion of fluid from the front thereof, the mixing of a portion of the live air charge with the spelled fluid and the concurrenttrapping of the mixture and the utilization of the trapped mixture in initiating and continuing the rearward stroke of the piston.

9. In combination in a pneumatic hammer, a cylinder, a piston operating therein, an exhaust passage in open and free communication with the forward end of the cylinder,

means intermediate the ends of the cylinder for delivering fluid under pressure from the cylinder to the passage, and a valve mechanism actuated by fluid within the exhaust passage for controlling the delivery7 end ol the exhaust passage.

l0. In combination in a pneumatic hammer, a cylinder, a free piston operating therein, an exhaust passage in open and vfree communication with the forward end of the cylinder, means intermediate the ends of the cylinder for delivering fluid under pressure from the cylinder to the passage and :i valve mechanism for controlling the delivery and discharge of fluid to and from the rear end of the cylinder and the discharge of fluid from the passage, responsive in operation to the action of the fluid within the passage.

ll. In combination in a pneumatic tool, a

Werl-:ing cylinder having a fluid inlet and a fluid outlet port at the rear end thereof, a free piston operating in said cylinder, a valve casing having a fluid discharge port, a chamber in free communication with the forward end of said cylinder, means for delivering fluid under pressure from said cylinder to said chamber, and a valve located in said valve casing and responsive to pressure within said chamber for controlling the delivery and discharge of air from said cylinder through said inlet and out-let ports and communication between said chamber and said discharge port.

l2. In combination in a pneumatic tool, a cylinder, a free piston operating therein, a chamber extending longitudinally of said cylinder and in open and free communication with the forward end thereof, a valve located at the rear end of said piston and responsive to fluid pressure within said chamber for controlling the delivery of mo tive fluid to the rear end of the cylinder, the discharge of fluid from the rear end of the cylinder and the discharge of fluid from said chamber, and means for admitting high pressure fluid from said cylinder to said chamber to shift said valve thereby cutting off the discharge of fluid from said chamber and the delivery of high pressure fluid to said cylinder.

13. In combination in a pneumatic tool, a working cylinder having a fluid inlet port and a fluid outlet port at its rear end, a free piston within said cylinder, a chamber extending' longitudinally of said cylinder and in free communication with the forward end thereof, a valve casing having a fluid discharge port, a valve within said casing and responsive to Huid pressure within said chamber for controlling said fluid inlet port, communication between said fluid outlet port and said discharge port and communication between said chamber and said discharge port, and means for delivering high pressure fluid from said cylinder to said chamber to actuate said valve to close communication between said chamber and said exhaustport and to initiate and continue the rearward movement of said piston.

14. in combination in a pneumatic tool, a cylinder having fluid inlet and exhaust ports at the rear end thereof, a free piston Within said'cylindei, a chamber in open communication With the forward end of said cylinder, a valve subjected to pressure Within said chamber, and controlling said ports and communication between said chamber and the atmosphere, means for admitting high pressure fluid from said cylinder to said chamber, to move said valve to close said chamber and said inlet port and to open said exhaust port,and means controlled by said piston for occasioning a movement of said valve to open said chamber, said inlet port and to close said exhaust port.

' l5. In combination in a pneumatic tool, a working cylinder having a fluid inlet port and a `fluid outlet port at the rear end there* of, a free piston operating` Within said cylinder, an exhaust passage for the forward end of said cylinder, ak valve for controlling vthe discharge of fluid from said passage and the delivery of fluid through said inlet and outlet ports, and means 'for delivering high pressure fluid from saidV cylinder behind said piston to said exhaust passage.

In testimony whereof, I haveV hereunto set my hand.

FRANK L. O. WADSWORTH. 

